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Chapter 41 Magnetism
2nd Year Science
Ms. Shevlin
Objectives:
To discuss what magnetism is
To investigate how magnetic forces work
To examine how magnets work
To carry out an experiment to show the magnetic
field around a bar magnet using iron filings and
plotting compasses
To discuss places where magnets are used in
everyday life
A magnet is a piece of metal that can attract other
substances to it.
Magnets were first discovered about 2,500 years
ago.
Man-made Magnets
Only three magnets from the periodical table can
be magnetised e.g. iron, nickel & cobalt.
Strong magnets can be made by mixing elements
to form alloys e.g. steel = carbon + iron
Alnico = aluminium + nickel + iron + cobalt
What is magnetism?
• Magnetism is a FORCE.
How do magnetic forces act?
• Magnetic forces can be attractive or
repulsive
• Like poles repel.
• Unlike poles attract.
Where do we use magnets?
• The simplest use of magnets is in the compass.
• When a magnet is free to move it lines up northsouth.
• This happens because the earth is a giant magnet.
Can you make a compass?
• These are two easy ways to make your own
compass.
• Give one a try but remember you must
magnetise your needle first.
Are all materials magnetic?
• Three metals are attracted to magnets and
can be made into magnets themselves.
• These metals are iron, cobalt and nickel.
• Other metals that are mixtures of these
metals or alloys are also attracted to
magnets.
• Find out which materials you have contain
one or more of these metals.
What is a magnetic field?
• As we bring two like poles of
a magnet close together we
can feel the magnets
pushing away from each
other.
• The magnetic force acts
around the magnet.
• The area around the magnet
where we can detect a
magnetic force is called the
magnetic field.
Does the earth have a magnetic field?
• Since the earth is a giant magnet it also has a magnetic
field.
What do I know about magnets?
•
•
•
•
•
Magnetism is a force.
Magnets have two poles a north and a south.
Like poles repel.
Unlike poles attract.
When magnets are free to move they line up northsouth.
• Magnets are made from or contain iron, cobalt and
nickel.
• The area in which a magnetic force can be detected is
called the magnetic field.